46 
Psyche 
[September 
rate u-scripta and arcuata, since this information lends more significane 
to the behavioral studies. There follows a discussion of the ethology 
of the two colonies studied and finally a brief statement of conclusions. 
T he studies of the Texas colony were made with the assistance of a 
grant from the National Science Foundation, while those of the New 
Mexico colony were made during tenure of a fellowship from 
the John Simon Guggenheim Memorial Foundation. I am indebted 
to Dr. M. A. Cazier, Director of the Southwestern Research 
Station of the American Museum of Natural History, for making 
available the facilities of that station during the summer of 1959. I 
am also indebted to Drs. Cheng Shan Lin and Oliver S. Flint for as- 
sisting me in the field work on the Texas colony. The dipterous prey 
of the Bembix have been identified by the following specialists, to all 
of whom I am much indebted: W. L. Downes, R. H. Foote, M. T. 
James, C. Martin, R. H. Painter, L. L. Pechuman, H. J. Reinhard, 
C. W. Sabrosky, Y. Sedman, H. V. Weems, and W. W. Wirth. 
Morphological Considerations 
The important structural features of Bembix u-scripta and arcuata 
are given as follows by Parker (1917, 1929) : 
1. Ocelli unusually well developed and apparently functional 
(posterior ocelli with lenses clear, convex, circular except truncated 
laterally; anterior ocellus in form of a fairly wide transverse band). 
2. Second transverse cubital vein of front wing only slightly 
curved (in other species of Bembix it is sharply bent). 
3. Male with basal segment of middle tarsus distinctly curved, 
its inner surface beset with several stout spines; middle femora of 
male dentate, middle tibiae ending in a spine-like process. 
4. Male with abdominal sternites devoid of processes, but seventh 
with a pair of carinae which diverge basally. 
5. Labrum with a small median elevation (both sexes). 
6. Basal segment of front tarsus with an unusually large number 
of comb-spines (8-10) (both sexes). 
7. Scape of male much thickened. 
8. Pygidium of female slightly rugose and with strong lateral 
ridges. 
9. Pattern of yellow maculations unusually strongly developed. 
To these nine characters should be added another: 
10. Apical tergite of male with deep longitudinal lateral incisions 
which cut off a pair of appendages which much resemble the parameres 
of the genitalia. 
